Application of a diffusive passive water sampler to investigate the fate of organic pollutants in wastewater treatment works and comparison of engineered and natural treatment systems

Abstract

Compliance with Environmental Quality Standards for organic pollutants is paramount to healthy living and sustainability of aquatic organisms. The European Commission expects that certain standards should be met by members' state although the procedure or operational approach to meeting the standards is left with each member state. For some members, the costs of monitoring their surface water basins are excessive and as such, meeting the expected standards has been a challenge. This study was designed to investigate and further validate the use of passive water as investigative tools to measure the presence of organic pollutants in our environment as well as a comparison of engineered and natural treatment systems. Various studies have been undertaken with the use of Diffusive Gradient in Thin-film passive samplers to validate their potential wide range applications including in wastewater treatment works. The study investigated nature-based treatment technology as a viable alternative to the conventional treatment works for the removal of personal care product ingredients and antibiotics from the environment. Removal efficiency rates and chemical partitioning in the treatment works were also considered between the sludge cakes that are used by the farmers as organic manure and the removal process. DGT samplers containing HLB gels for personal care products and Amberlite XAD-18 for antibiotics were deployed for various aspect of this study. This study investigated the performance of passive sampler in the selected 6 nature-based treatment technologies and 3 conventional treatment works in Italy where eight antibiotics were detected out of 23 that were investigated. Removal of Clarithromycin ranged from < 1% to 100% for nature-based technologies and < 1% to 100% for the conventional systems. Removal rates of other pharmaceutical ingredients are up to 100% in both systems, but the SPD had an influent/effluent concentration of 91 ngL-1 to 810 ngL-1 in the Nature-based system. Removal of personal care products between the two systems was very comparative where average removals of preservatives in nature-based and conventional treatment was 72% to 58%, Antioxidants were 57% to 44% except for TCC in both systems and 47% to 57% except for Nonylphenol respectively. High concentrations of TCC and NP at the effluents may have resulted from the degradation of parents’ compounds that were not detected at the influents channels. However, some low removal rates in some of the treatment systems may have resulted from low degradation or high sorption affinity to organic matter since DGT only measure dissolved compounds. Sampling campaigns in wastewater treatment works in North West England focused more on DGT for long-term monitoring of organic pollutants as well as partitioning in the treatment works. A 52-week sampling campaign at the influent and effluent channels confirmed a high removal efficiency of personal care products. The overall average removal rates in this site over the 52 weeks ranged from < 1% 4-T-OP to 92% MEP. However, 28 days sampling to investigate the chemical partitioning at the same works confirmed less variability in the treatment works with PCPs removal efficiency of 14% to 100% compared to the long-term monitoring. A further study was conducted on the sludge cake that is gaining a wide acceptance in agricultural use being the most economical method for disposal which ultimately reduces costs in terms of farmers investments on enhancing the productivity of their land. The major associated costs are the transportation and spreading/soil modification with the cakes which is far less than the costs of incineration which a common disposal method in many European countries. The laboratory study of 21 days deployment period compared the competing removal mechanisms of degradation and sorption of chemicals. iii Current regulations reduce the considerable effect of biohazard on the agricultural land by leaving a substantial time of not less than 28 days after amending the soils before cultivation. Some compounds degrade swiftly while uptake of PHBA increased from 859 ngL-1 to 2,114 ngL-1 over the period, which shows that PHBA would need more than 21days to fully desorb and degrade. Having considered other passive samplers to include Chemcatcher, POCIS and grab sampling, the size of DGT and its simple operations procedures was very helpful in delivering this study.